Week 4 Histology - Lymphoid Organs

Question 1

Where along the GI tract would one find Peyer patches?

Answer 1

Ileum and appendix

Question 2

What is the difference between a primary lymphoid follicle and a secondary follicle?

Answer 2

Secondary follicles have B cells undergoing VDJ recombination and proliferation that results in decreased cell density at the center of the follicle. Therefore, secondary follicles stain lighter in the center and darker around the peripheral mantle.

Question 3

Which lymphoid organs have a paracortex? What cell type(s) are predominantly found in the paracortex?

Answer 3

Lymph nodes - T cells are mostly found here

Question 4

Through what structures do lymphocytes enter lymph nodes?

Answer 4

High endothelial venules (HEVs)

Question 5

What cell types are found in the medullary cords of a lymph node?

Answer 5

T cells, B cells, plasma cells

Question 6

Name 1-4.

Answer 6

1. Primary follicle
2. Secondary follicle
3. Germinal center
4. Mantle/cap

Question 7

Identify the white pulp (ignore the arrows). What cells and structures are found in white pulp?

Answer 7

The purple stuff is the white pulp. White pulp consists of lymphoid nodules with B cells and peri-arteriolar lymphoid sheaths surrounding central arterioles.

Question 8

This is a tonsil. Identify the structures at the arrows, green asterisks, and black asterisks.

Answer 8

Arrows are pointing to the CT capsule.

Green asterisks are at secondary follicles.

Black asterisks are in a crypt.

Question 9

Which lymphoid organ is this? Name the area on the left (#1), the area on the right (#2), and the structures indicated by #3.

Answer 9

Spleen

1 - red pulp

2 - white pulp

3 - central arterioles

Question 10

What are those outlined structures? Where are these found?

Answer 10

Hassall’s corpuscles - unique to the thymic medulla!

Question 11

What cell types would you find in the cords of the red pulp of the spleen?

Answer 11

Stromal cells, macrophages, RBCs